Thermostatic control for electric heaters



June 11, 1929. YN s 1,717,155

THERMOSTATIC CONTROL FOR ELECTRIC HEATERS Filed Aug. 29, 1923 P p Svwcmboz LEE P HYNE5 @51 hub a t/[707M013 Patented June 11, 1929.

UNITED STATES PATENT OFFICE.

LEE 1. HYNES, OF ALBANY, NEW

YORK, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

CONSOLIDATED CAR-HEATING COMPANY, INC., OF ALBANY, NEW YORK, A CUR- PORATION OF NEW YORK.

Application filed August 29, 1023.

For a detailed description of the present form of my invention, reference may be had to the following specification and to the accompanying drawings forming a part thereof, wherein Fig. 1 is a front view,

Fig. 2 a circuit diagram of my device and Fig. 3 is a sect-ion of the magnet and condenser.

In apparatus for the automatic control of an electric-heater switch by a thermostat it is important to protect the contacts of the thermostat from injury by an are either at the opening or closing of such contacts. Such an arc is caused by the reaction of an Y electromagnetic coil which may be contained in the circuit whenever the circuit is opened and sometimes damage may occur when the circuit is closed. The customary method of protecting circuit contacts under such circumstances is to place a condenser in shunt to the contacts and to the magnet, the capacity of the condenser serving to eliminate at the contacts the induced or reactionary voltage from the magnet. I11 the case of electric-heater switches this customary method has not proved wholly reliable by reason of the deficiencies and improper proportions of the condenser. \Vherefore the more usual practice has been to make the current in the thermostat circuit extremely small and employ it merely to operate a relay which, in turn, operates less delicate contacts in the circuit of the heater-switch magnet. By making use of the improved forms of condenser developed for radio work, I am enabled to adequately control the are at the thermostat contacts by a properly proportioned condenser without resort to a relay. I also have devised an arrangement in which the heater-switch is closed instead of opened by the pull of its op-- era ting magnet. These features serve to simplify and cheapen the construction and also to improve its operation. In particular, the aforesaid result of a car-heating system controlled directly by a thermostat without resort to a relay has been successfully achieved for the first, and only, time in the history of this art so far as I am aware, hundreds of my devices being in practical operation. This result is due to the organization herein described wherein three branch circuits containing respectivel (a) the switch-closing magnet, (b) the t ermostat contacts (0) a ground. This thermostat Serial No. 659,932.

specially adjusted condenser, are all together in series with a high-resistance (e. g. 6000 ohms) and that system of circuits then placed in parallel with a circuit containing the electric heaters and the controlling contacts therefor. \Vherefore I claim novelty in this result or function as well as in the organization by which it has been achieved. Other features will also be described hereinafter.

Referring to the drawing, 2 represents a box or casing containing my apparatus and provided with a hinged cover 3, which may be locked at 4, as indicated in the tlrawing. On the front of the box is a window separated a slight distance from the front wall. of the box. Behind the window and in front of the box wall is an indicator arm S which is secured to the armature of the switch-operating magnet by a lateral offset which passes thorugh a slotted opening (3 in the front wall of the box. A blade on the end of S covers one or the other of the words Off and On inscribed on the box wall, accordin as the magnet is energized, to close the heater circuit, thereby lifting the shield to disclose the word 011, while covering the word Off, or deenergized to open the heater circuit, thereby draping the shield to cover the word On and disclose the word Off. Referring to the circuit diagram of Fig. 2, the current from trolley V under a voltage of 600 passes through the main fuse T and goes to the terminal A. From A the heater current goes through the blow-out coil B to contact O, and, if the switch-operating coil 13 is energized and spring D thereby t ought into engagement with C, it goes to the two branch sets of heaters V by way of the respective heater fuses F, F, and thence to ground. There also extends from terminal A a branch opera ting circuit through resistance H, which has, for example, 6000 ohms, to magnet J having 600 ohms, to terminal K and ground. So long as the heaters give a normal temperature to the apartment and the thermostat circuitis open, this operating circuit will cause magnet J to lift its armature and hold the heater circuit closed. When, however, the ten'iperature produced by the heaters exceeds a predetermined degree, the thermostat O will. close its circuit, which extends from L to fuse G, to point N and thence through the thermostat O to circuit will be of such low value as to divert from magnet J is to be used by enough of the current admitted through resistance H toshort-circuit the magnetand cause it to open the heater circuit at O by dropping its armature. Any are that may occur between C and D will be suppressed by blow-out magnet B. I connect across the terminals of ma net J a condenser P which, for the stated trolley voltage and the resistance of H and magnet J, should have a capacity of about .0005 microtarads. This condenser shunts both magnet J and the thermostat O,

and, it it is of the proper capacity, such as above stated, will absorb the induced voltage of the magnet when the thermostat contacts are opened and have no reactionary voltage of its own when the thermostat contacts are closed.

I also provide a manual switch R by which a connection may be made at will between the terminals N and K through which the thermostat circuit will be grounded whenever the switch is closed. This switch B is provided with a handle R on the outside ofthe box and the operator for turning the heaters on or off. Thus by turning handle R to the left, and thereby closing switch R, the magnet J will be short circuited just as it would be if the thermostat circuit were grounded by the thermostat itself in the manner heretofore described, the heaters then being open-circuited and turned off; while by turning R to the right such short-circuit is removed and the switch-magnet permitted to operate under control of the thermostat, as I have described. In the event of the breaking of the thermostat, the switch It may be used to control the heaters manually until the broken thermostat is replaced. denser P is in practice built into the magnet J, being placed on the outside thereof as shown in Fig. 3 and wrapped around it under a winding Y of cord or tape with its terminals permanently secured to those of the magnet. It thereby becomes unnecessary to install the condenser separately as an additional member of the organization.

What I claim as new and desire to secure by Letters Patent is:

V 1. An automatic controldevice for an elec- The concircuit, a branch circuit, a high-resistance magnet in said branch circuit controlling said switch, a resistance in said circuit in series with the magnet, a circuit shunting said magnet and containing a thermostatic switch and a condenser of a capacity adjusted to said resistance and the resistance of the magnet with respect to the line voltage located in shunt to both said magnet and the thermostatic switch.

2. An automatic control device for an electric heater, comprising a switch in the heater circuit, a branch circuit, a high-resistance magnetin said circuit controlling said switch, a resistance in said branch circuit in series with the magnet, a circuit shunting said magnet and containing a thermostat, a condenser of a capacity adjusted to said resistance and to the resistance of the magnetwith respect to the line voltage located in shunt to both said magnet and the thermostat, and a hand switch in a circuit-also shunting both the magnet and the thermostatic switch.

An automatic control device for anelectric heater comprising a switch in the heater circuit, a branch circuit, a high-resistance magnet in said branch circuit controlling said switch, a resistance insaid branch circuit in series with the magnet, a circuit'shunting said magnet and containing a thermostatic switch and a condenser mounted on them-agnet and contained in a circuit shunting both the magnet and the thermostatic switch.

4;. An atmosphere-hea-ting regulator comprising an electric heater, a switch in the heater circuit which is closed magnetically and opened mcchanicall y, a plurality of. shunt circuits in parallel with the heater circuit one containing the switcl1closing magnet, one containing a condenser and one containing contactswhich are controlled by a thermostat together with a comparatively high resistance in series with the said shunt circuits.

Signed at Albany, county of Albany and State of New York, this 16th day of August, 1923.

LEE P. HYNES. 

